1. Field of the Invention
This invention relates to a multi-directional input key and a key input device for a pushbutton switch for performing an input operation on an electronic apparatus, such as a portable information terminal apparatus like a mobile telephone or PDA, an AV apparatus, a car navigation system, or a remote controller for various apparatuses.
2. Description of the Related Art
An electronic apparatus is equipped with a number of input keys for executing the functions thereof. With the recent increase in the number of functions of electronic apparatuses, there has been developed a system in which a single input key is used for different input purposes.
As an example of such a system, FIG. 16 shows a mobile telephone 1, which is equipped with an input key group 2 consisting of various keys with figures, symbols, patterns, etc. As shown in FIG. 17, there is provided above the input key group 2 an input key 3 protruding through a mounting hole 1b of a casing 1a. This input key 3 is generally called a multi-directional input key and constructed as follows. A stick-like key top 5 formed of hard resin is joined with adhesive (not shown) to a key sheet 4 formed of a rubber-like resilient member such as silicone rubber or thermoplastic elastomer. Thus, through resilient deformation of the key sheet 4, the key top 5 is capable of being tilted in all directions of 360 degrees. Normally, the key top 5 is tilted upwards, downwards, to the right, and to the left, whereby one of a plurality of selection items displayed on a display screen 6 can be selected, and a cursor displayed on the display screen 6 can be moved upwards, downwards, to the right, and to the left. And, to make it possible to perform such operations, the input key 3 is equipped with contact input portions 7 formed on the key sheet 4 and consisting of conductive ink or the like, and board contacts 8 formed on a circuit board 8. As shown in FIG. 17, as the key top 5 is tilted in the different directions, these contact portions and board contacts come into contact with each other to be thereby brought into conduction.
In this way, the input key 3, which allows multi-directional input, advantageously meets the mutually contradictory requirements in an electronic apparatus: an increase in the number of functions and space saving. Thus, it is used in various electronic apparatuses inclusive of the mobile telephone 1. However, from the viewpoint of operability, the results obtained therefrom up to now are not always satisfactory.
That is, as long as the input key 3 is tilted in the normal tilting directions through depression, the board contacts 9 of the circuit board 8 can be brought into conduction. However, the very fact that it is capable of being tilted in all directions of 360 degrees allows the input key to be easily tilted obliquely in the wrong directions. In such cases, not only the board contact 9 of the circuit board 8 to be brought into conduction for input operation, but also another board contact 9 adjacent thereto is likely to be brought into conduction, with the result that input operation has to be conducted again. Moreover, there is a danger of the mobile telephone 1 might be erroneously operated.
This problem of erroneous input also occurs in a case in which the input key 3 allows oblique input through simultaneous conduction of adjacent board contacts 9 as in the case of the upper and right contacts, the upper and left contacts, the lower and right contacts, and the lower and left contacts. Further, this applies not only to the input key 3, called a multi-directional key, but also to an input key in which operating points are indicated by triangular symbols or the like at upper, lower, right, and left positions on a flat depressing operation surface, an input key called a seesaw key having a depressing operation surface of, for example, a rectangular or elliptical configuration, and an input key called a mono-directional key having only one operating point on a rectangular or elliptical operation surface. Thus, there may be cases in which input is not correctly effected on the right board contact 9 even when the operator believes he has tilted the input key in a normal tilting direction.